The Children's Hospital of Philadelphia (CHP) is a primary treatment center for children with malignant diseases. It also has been designated a Pediatric Cancer Research Center (USPHS Grant # 14489). As a member institution of the Children's Cancer Study Group (CCSG) the study and treatment of Pediatric Oncologic disorders will be pursued via the Phase II and III protocols of CCSG. Chemotherapy and immunotherapy will be utilized alone or in conjunction with surgery and/or radiation therapy, as indicated by the study protocols, in efforts to devise more effective and less toxic methods of improving survival in children with leukemia and solid tumors. The Children's Hospital of Philadelphia is one of the four CCSG institutions performing bone marrow transplantation as a mode of therapy for patients with Acute Non-Lymphocytic Leukemia (ANLL). Co-investigators from Surgery, Pathology, Diagnostic Radiology, Radiation Therapy, Dentistry and Infectious Diseases will participate in the development and conduct of these studies. Through the use of the Intergroup Study mechanism, collaboration with other Cooperative Cancer Study Groups will achieve statistically valid study of the less frequently occurring malignancies. The CHP will also actively participate in the Group's efforts in accessing the late effects of cancer therapy.